If two parametrically-coupled fields, with the frequency of the probe p wave twice the frequency of the support s wave, are applied to a metal plasma, the non-linearity of the Boltzmann equation affects the permittivity. Based on the solution of the Boltzmann equation for the bichromatic problem, an analytical expression for the permittivity was derived. The amplitudes and the relative phase of the p and s waves can be adjusted to suppress the dielectric loss to almost zero within a narrow frequency band. If this frequency band overlaps with a negative-refractive-index band of a composite metamaterial, which contains a metallic component, the optical losses can be reduced by a factor of ∼ 30, with a figure of merit exceeding 100. An isotropic metamaterial comprising spherical Au and SiC nanoparticles can show that effect.